Very recently it has been proposed to prevent possible contamination of the soil and of ground water underneath waste dumps by creating a basement-like cavity underneath the dump.
Such a basemented dump is intended for the purpose of reliably catching and collecting seepage, of being able to examine the sealing system for its reliability at any time and in a simple manner, and to detect and repair damage quickly. It is furthermore intended to permit leakage or seepage to be trapped by a second system in case of damage.
Sealing by means of a basement-like cavity is many times more expensive and complex than the seals used heretofore, but it provides the advantage of being able in a simple manner to inspect the seals visually and make them secure at any time.
In one known embodiment, the dumped material rests on a concrete slab which has a basement underneath it. The basement can be walked through. The concrete structure can be made of poured concrete or built up of precast blocks. The main sealing function is performed by an overhead plastic membrane (similar to a suspended ceiling) which conforms as tightly as possible to the underground roof and has elastic properties.
The top surface of the platform is divided into individual fields by raised boundaries. The seepage water is collected field by field and analyzed for quality.
These known proposals do not take into consideration the great deformations to which such a structure is exposed under the burden of the dumped material on an always more or less compressible subgrade. The consequences of these deformations are added tensions and possibly also cracking in the structure, which can defeat its purpose. In view of this cracking, which is considered inevitable, the suspended water-tight cover is therefore arranged underneath the actual concrete roof, and the seepage penetrating through the cracks and seams of the structure are caught by this cover and removed.
The sealing problem cannot be solved in this manner, because the seepage, which is laden with a great variety of harmful substances, would attack the load-bearing structure itself, beginning at the seams, and possibly destroy it.
Another danger which has not been recognized and dealt with accordingly in the known floor construction results from the great horizontal forces which can act on the structure, for example, in the case of an earthquake.